Catalyst and process for the polymerization of alpha-olefins

ABSTRACT

A novel catalyst and process for producing crystalline polypropylene and its copolymers with other alpha-olefins which can substantially reduce the amount of low-molecular-weight and amorphous polymers formed without reduction in the polymerization rate. This novel catalyst and process are useful in slurry polymerization, bulk polymerization and polymerization techniques in which polymerization is accomplished utilizing monomer substantially in the vapor phase.

United States Patent Karayannis et al.

[ Dec. 16, 1975 CATALYST AND PROCESS FOR THE POLYMERIZATION OF ALPHA-OLEFINS Inventors: Nicholas M. Karayannis, l-linsdale;

Missak Khelghatian, Naperville; Sam S. Lee, Hoffman Estates, all of I11.

Assignee: Standard Oil Company, Chicago, 111.

Filed: Aug. 27, 1973 Appl. No.: 391,608

US. Cl. 260/881; 252/429 B; 260/882 R; 260/937; 260/949 CB; 260/949 CC; 260/949 CD Int. Cl. B01J 31/02; C08F 210/00; C08F 212/00; C08F 110/02 Field of Search 260/937, 88.2 R

References Cited UNITED STATES PATENTS 10/1960 Coover et al. 260/937 6/1969 Watt 252/429 3/1970 Stedefeder 260/937 3,736,307 5/1973 Perry 260/882 R OTHER PUBLICATIONS Doak and Schrage, in Crystalline Olefin Polymers Part I (lnterscience, 1965) pp. 366-371.

Coover and Joyner, J. Polymer Science, Part A, 1965, 3, 2407-2424.

Primary ExaminerJoseph L. Schofer Assistant Examiner-A. L. Clingman Attorney, Agent, or FirmReed F. Riley; William T. McClain [57] ABSTRACT 14 Claims, No Drawings CATALYST AND PROCESS FOR THE POLYMERIZATION OF ALPHA-OLEFINS SUMMARY OF THE INVENTION This invention relates to a novel catalyst and process for the polymerization of propylene and its mixtures with other alpha-olefins to produce normally-solid, crystalline polymers, and more specifically. to a novel catalyst and process for polymerization of propylene and its mixtures with other alpha-olefins which produces normally-solid, crystalline polymeric products wherein coproduced low-molecular-weight and amorphous polymers are substantially reduced while maintaining the polymerization rate.

In accordance with the instant invention, propylene and its mixtures with other alpha-olefins are polymerized to normally-solid, crystalline polymers using a slurry, bulk or vapor technique at monomer pressures of about atmospheric pressure and above and moderate polymerization temperatures with a catalyst system comprising: (a) an alkyl aluminum compound, (b) a chloride of titanium, and (c) a hydrocarbyltin sulfide and trihydrocarbylphosphite. The polymeric products produced using the above described catalyst can contain amounts of low-m'olecular-weight and amorphous components, as measured by extraction using n-hexane, as low as about one percent of the total polymer yield.

BACKGROUND OF THE INVENTION Polymers of alpha-olefins prepared in the presence of ionic catalyst systems, as for example polypropylene prepared using a catalyst comprised of diethylaluminum chloride and titanium triehloride, contain greater or lesser amounts of low-molecular-weight and amorphous components which, when taken alone, are viscous oils or soft, tacky solids. The presence of these alkane-soluble materials in the polymers leads to difficulties during the fabrication of products therefrom and to inferior physical properties in the finished items, and hence are almost always removed in commercial processes for the production of polypropylene. Production of these components leads to an economic disability for the polymerization process as they have little usefulness and extraproeess steps are required to remove them from the commercial product.

In the past a number of materials and combinations thereof have been reported in the patent literature as useful components to reduce the alkane-soluble fraction produced during the polymerization process. Among these materials have been amines, amine oxides, ethers and organic phosphites. Some organotin oxides and sulfides have been described as well with oxides showing a far greater effect on Solubles reduction than the corresponding sulfides. Generally, such materials give ionic catalyst systems which, when used to polymerize an alpha-olefin such as propylene, result in a reduction of the polymerization rate as well as the Solubles so that an increase in the proportion of crystalline polypropylene formed is obtained but at the expense of the total polymerization yield.

Now it has been found that by using an ionic catalyst with a (c) component composed of a trihydrocarbylphosphite and a hydrocarbyltin sulfide, a substantial reduction of Solubles can be accomplished while maintaining or improving the total yield ofpolymer. In addition, the instant catalyst can give an improvement in a 2 solventless polymerization process wherein the olefin is polymerized directly from the vapor or liquid phase. The instant (c) component may also be used for olefin polymerizations wherein a supported organometallictransition metal catalyst is employed.

STATEMENT OF THE INVENTION Table l Slurry Polymerization of Propylene Comparison of Crystalline Rates and Solubles for Different Amounts of the (e) Component t Crystalline Rate BTS/TBP* (grams per gram TiCl;,) Solubles** (molar ratios) per hour (percent) *BTS represents bis-(triliutyltin) sulfide. TBP represents trihutyphosphite and Et. .AlCl represents diethylaluminum chloride.

Solubles was determined by filtering the solid product away from the polymerization medium. chopping in a blender with 2 liters of n-hexane and then with 2 liters of methanol and finally'washing the resulting solid polymer with 500 milliliters of n-hexane. The hexane portions were then combined and a ll) percent aliquot evaporated to dryness and the residue dried under vacuum at about 80C. Solubles is then l00 times the total soluble polymer divided by the total polymer produced.

***This polymerization used a different batch of the same aluminum reduced and activated TiCl; for which a control run (0/0) gave a Crystalline Rate of 930 and Solubles of l l l.

Table II Bulk Polymerization of Propylene Comparison of Crystalline Rates and Solubles for Different Amounts of the (c) Component Crystalline Rate BTS/TBP (grams per gram TiCl Solubles* (molar ratios) per hour) (percent) 0/0 L841 4.78 0/0337 L340 2.91 0/0675 L520 L16 0/l.0l L350 l.7 0.3/0 L542 2.53 0.l2/0.225 L957 1.80 0.242/0.225 1.677 4.58 0363/0228 L708 4.36

Solubles was determined by taking a 20 gram portion of the polypropylene product and washing it at room temperature with 200 milliliters of hexane containing 2 milliliters of methanol. The remaining polypropylene product was dried at C. for 3 hours. The filtrate was evaporated to dryness. Solubles is then I00 times the residue from evaporation divided by 20.

"his-(trihut vl)tin oxide was used in place of HTS in these two polymerizations.

Table III Bulk Polymerization of Propylene Comparison of Crystalline Rate and Solubles* for Difi'erent Amounts of the (0) Component Crystalline Rate BTS/TBP (grams per gram TiCl Solubles (molar ratios) per hour) (percent) 0/0 891 5.3 0.04/0 L005 4.3 0/057 L065 3.6 0.04/0.34 L265 2.l

Table ill-continued Bulk Polymerization of Propylene Comparison of Crystalline Rule and Soluhlcs* for Different Amounts of the (c) Component Crystalline Rate (grams per gram 'l'iCL, per hour) BTS/TBP (molar ratios) Solubles (percent) 0.04/05] Lllil 1.6

Tables ll andlll show similar results for polymerization of propylene using a bulk technique. 4 y

The (a),components useful for the herein described invention are alkylaluminum derivatives wherein the alkyl radical contains one to about six carbon atoms and, more specifically, are trialkyl aluminum compounds, mixtures thereof with an alkylaluminum dichloride or dibromide or a dialkyl-aluminum chloride or bromide, or dialkylaluminum chlorides or bromides. More preferably, the (a) component is trialkyl aluminum, mixtures thereof with either a dialkylaluminum chloride or an alkylaluminum dichloride, or a dialkyl aluminum chloride. Most preferably, a dialkylaluminum chloride is used. The amount of (a) component to be used is based upon the reactor size, the amount of (b) component used and the amount of olefin to be polymerized as is well known to one skilled in the art.

The (b) components useful herein are compounds of titanium. andv more preferably, the (b) component is titanium halide. Most preferably, the ('b) component is titanium trichloride. The amount of the (b) component used is based upon the amount and composition of the particular polymer to be made and is well known to one skilled in the art.

The phosphite part of the (0) component is usefully any trihydrocarbylphosphite and. more preferably, a trialkylphosphite where the alkyl group has one to about six carbon atoms or a triarylphosphite. Most preferably the phosphite part is a trialkylphosphite.

The sulfide part of the (c) component is usefully a sulfide of an alkyl, alkaryl or aryl tin radical. More preferably, this part isa sulfide of a trialkylor triphenyltin radical or a dialkylor diphenyltin radical. Most preferably, the sulfide part of the (c) component is a bis-(trialkyl)tin sulfide. By lower alkyl is here meant an alkyl group containing one to about six carbon atoms.

Usefully, the mole percentage of the phosphite and sulfide parts of the (c) component run from about 99 mole percent of the former and about 1 mole percent of the latter to about 1 mole percent of the former and about 99 mole percent of the latter. More preferably, the concentration range of the parts of the (c) component runs from about 85 to about mole percent of the phosphite part and from about 15 to about 80 mole percent of the sulfide partJ-Most preferably. the concentration range of the parts runs from about 85 to 40 mole percent of the phosphite part and from about 15 to about 60 mole percent of the sulfide part.

The amount of the (c) component depends upon the amount of (a) component to be used. Too little of the (0) component will not show an appreciable reduction of the low-molecular-weight and amorphous polymer produced. Too much of the (0) component will either reduce the polymerization rate or kill it completely depending upon the relative concentrations of each of the parts. In general. the (0) component amount can vary from about 0.1 mole percent of the (a) component to about 50 mole percent of the (a) component. More preferably. the range is about 0.5 mole percent of the (a) component to about 40 mole percent of (a) component and. most preferably, it may vary from about 0.5 mole percent of the (a) component to about 30 mole percent of the (a) component.

The parts of the (c) component may be added separately to the (a) and (b) components or, alteratively, they may be added together.

As is obvious to one skilled in the art. precautions should be taken to avoid oxygen and moisture contamination of the catalyst during its preparation and its transfer. Catalyst preparation can be carried out under an inert atmosphere using such gases as argon, nitrogen, helium, etc. Normally, during use no precautions need be taken as a positive pressure of monomer gas exists within the reactor.

The temperature at which the catalyst may be used is not critical and depends, in general, upon the particular (a) and (b) components which are used. However, at temperatures below about 0C. the rate of polymerization slows down and reactor residence times become unreasonably long whereas, at temperatures above about 120C, polymerization rates become too high and an increase in Solubles production is found. Preferably, the temperature range in which the catalyst can be used is about 2C. to about 95C. Most preferably, the temperature range is about 50C. to about C.

The process of the invention can be carried out at a monomer pressure of about atmospheric or above. Pressures of about 50 p.s.i.g. to about 600 p.s.i.g. or higher are preferred depending upon which polymerization technique is used.

The organic liquid employed as the polymerization medium in the slurry technique can be an aliphatic alkane or cycloalkane such as pentane, hexane, heptane or cyclohexane, or a hydrogenated aromatic compound such as tetrahydronaphthalene or decahydronaphthalene, or a high molecular weight liquid paraffin ormixture of paraffins which are liquid at the reaction temperature, or an aromatic hydrocarbon such as benzene, toluene or xylene, or a halogenated aromatic compound such as chlorobenzene, chloronaphthalene or ortho-dichlorobenzene. The nature of the reaction medium is subject to considerable variation, although the material employed should be liquid under the conditions of reaction and relatively inert. The hydrocarbon liquids are desirably employed. Other solvents which can be used include ethylbenzene, isopropylbenzene, ethyltoluene, n-propylbenzene, diethylbenzenes, monoand dialkyl-naphthalenes, n-pentane, n-octane, isooctane and methylcyclohexane. The preparative 'media employed in practicing this invention can be advantageously purified prior to use in the polymerization reaction by contacting the material, for example. in a distillation procedure or otherwise, with aluminum alkyl compound to remove undesirable trace impurities. Also, prior to polymerization the catalyst can be contacted advantageously with polymerizable alphaolefin.

The polymerization time is not critical and will usuallybe of the order of from 30 minutes to several hours in batch processes. Contact times of from one to four hours are commonly employedin autoclave-type reactions. When a continuous slurry process is employed. the contact time in the polymerization zone can also be regulated as desired, andin some cases it is not necessary to employ reaction or contact times much beyond one-half to one hour since a cyclic system can be employed by separation of the polymer and return of the solvent and excess monomer to the charging zone wherein the catalyst can be replenished and additional monomer introduced.

The invention is of particular importance in the preparation of highly-crystalline polypropylene. although it can be used for polymerizing propylene and its mixtures with other alpha-olefins of up to about eight carbon atoms. lt is useful for preparing pure-block. tenninal-block or multi-segment types of copolymers of ethylene and propylene or propylene and other alphaolefin monomer wherein the majority of the polypropylene is still substantially crystalline. Such copolymers can contain up to about twenty weight percent of another alpha-olefin depending upon the copolymer type. The pure-block copolymer may be composed of two different blocks or may be of the types ABAB etc. or ABCABC etc.

The process and catalyst of this invention" are normally used with an additive to control moleculanweight such as dialkyl zinc compounds or hydrogen, preferably hydrogen. Solid polymers having molecular weights greater than about 50.000 andless than about 5.000.000 result thereby. The amount of hydrogen to be used depends upon the melt index and molecular weight distribution to be obtained and is well known to those skilled in the art. I

While'the invention is described in connection with the specific Examples below, it is to be understood that these are for illustrative purposes only. Many altematives, modifications and variations will be apparent to those skilled in the art in the light of the below Examples and such alternatives, modifications and variations fall within the scope and spirit of the appended claims.

EXAMPLE I All polymerizations in this Example were carried out in a 1 gallon reactor using 1,500 milliliters of hexane as a preparation medium in .two hour runs at 160F and 250 p.s.i.g. propylene pressure. A 3 p.s.i.g. hydrogen pressure was employed. Aluminum reduced and activated TiCl was used with Et AlCl.

Solubles was determined by filtering the solid product away from the polymerization medium, chopping in a blender with 2 liters of n-hexane and then with 2 liters of methanol and finally washing the resulting solid polymer with 500 milliliters of n-hexane. The hexane portions were then combined and a percent aliquot evaporated to dryness and the residue dried under vacuum at about 80C. Solubles is then 100 times the total soluble polymer divided by the total polymer produced.

The results are shown in the Table below.

TABLE IV Crystalline Rate TABLE lV-continued Crystalline Ratc Et AlCl/TiCln/BTS/TBP (grams per gram Solubles (Molar Ratios) TiCl per hour) (percent) 4.5 l [0.04/0075 X97 4.) 7X3 4.l

The results below were obtained. using another variety of aluminum reduced and activated TiCl Crystalline Rate All polymerizations were carried out in a 1 liter reactor using 13.3 milliliters of hexane in 2 hour runs at 160F. using 675 milliliters (460 p.s.i.g.) of liquid propylene and 3.5 p.s.i.g. of hydrogen pressure. Aluminum reduced and activated TiCl was used with EtgAlCl.

Solubles was determined by taking a 20 gram portion of the polypropylene product and washing it at room temperature with 200 milliliters of hexane containing 2 milliliters of methanol. The remaining polypropylene product was dried at C. for 3 hours. The filtrate was evaporated to dryness. Solubles is then 100 times the residue from evaporation divided by 20.

The results are shown in the Table below.

TABLE V Crystalline Rate The results below were obtained using another variety of aluminum reduced and activated TiCl EXAMPLE Ill All polymerizations were carried out in a 2 liter reactor using about 18.2 p.s.i.g. hydrogen and 1,300 cubic centimeters of liquid propylene in 2 hour runs at F. A 13 milliliter amount of n-hexane was added to the reactor with the catalyst. Aluminum reduced and activated TiCl was used in 0.1 gram amount and the Et- AlCl/TiCl mol ratio is 4/ 1.0 for each run.

Solubles was determined by taking a 20 gram portion of polymer product, treating it with 250 milliliters of n-hexane at 160F. for 2 hours, washing the residue with 100 milliliters of n-hexane, combining the wash and extract liquids and removing the hexane at ambient temperature in a vacuum ovehJThe extracted product was then dried at 160F. for 2 hours. Solubles is 100 times the residue remaining after evaporation of the wash and extract liquids divided by 20.

Crystalline Rate What is claimed is: l. A composition which comprises: a. a material selected from the group consisting of a trialkyl aluminum. a mixture of trialkyl aluminum and an alkylaluminum dichloride or dibromide, a mixture of a trialkyl aluminum and a dialkylaluminum chloride or bromide. and a dialkylalumimum chloride or bromide, titanium trichloride, an alkyltin sulfide, and a trihydrocarbylphosphite. A composition which comprises: a material selected from the group consisting of a trialkyl aluminum, amixture of a trialkyl aluminum and an alkylaluminum dichloride,-a mixture of a trialkyl aluminum and a dialkylaluminum chloride, and a dialkyl-aluminum chloride, titanium trichloride, an alkyltin sulfide, and a trihydrocarbylphosphite. A composition which comprises: a dialkylaluminum chloride, and titanium trichloride, and an alkyltin sulfide, and a trihydrocarbylphosphite. The composition of claim 1 wherein (c) is a bis- (trialkyl)tin sulfide and (d) is a trialkylphosphite.

5. The composition of claim 2 wherein (c) is a bis- (trialkyl)tin sulfide and (d) is a trialkylphosphite.

6. The composition of claim 3 wherein (c) is a bis- (trialkyl)tin sulfide and (d) is a trialkylphosphite.

Anne-man oesppglogr 7. The composition of claim 6 wherein (c) is his- (tributyUtin sulfide and (d) is tributylphosphite.

8. A process wherein propylene or propylene and at least 1 other alpha-olefin of from 2 to about 8 carbon atoms is contacted by at least a catalytic amount of a composition to form highly-crystalline polypropylene or copolymer wherein the polypropylene is still substantially crystalline comprising:

a. a compound selected from the group consisting of a trialkyl aluminum. a mixture of a trialkyl aluminum and an alkylaluminum dichloride or dibromide, a mixture of a trialkyl aluminum and a dialkylaluminum chloride or bromide, and a dialkylaluminum chloride or bromide,

b. titanium trichloride,

c; an alkyltin sulfide, and

d. a trihydrocarbylphosphite.

9. A process wherein propylene or propylene and, at least I alpha-olefin of from 2 to about 8 carbon atoms is contacted by at least a catalytic amount of a composition to form highly-crystalline polypropylene or copolymer wherein the polypropylene is still substantially crystalline comprising:

a a compound selected from the group consisting of a trialkyl aluminum, a mixture of a trialkyl aluminum and an alkylaluminum dichloride, a mixture of trialkyl aluminum and a dialkyl-aluminum chloride and a dialkylaluminum chloride,

b. titanium trichloride, 0. an alkyltin sulfide, and

d. a trihydrocarbylphosphite.

10. A process wherein propylene or propylene and at least 1 alpha-olefin of from 2 to about carbon atoms is contacted by at least a catalytic amount of a composition to form highly-crystalline polypropylene or copolymer wherein the polypropylene is still substantially crystalline comprising:

a. a dialkylaluminum chloride,

b. titanium trichloride,

c. an alkyltin sulfide, and

d. a trihydrocarbylphosphite.

11: The process of claim 8 wherein (c) is a bis- (trialkyl)tin sulfide and (d) is a trialkylphosphite.

' l2.The process of claim 9 wherein (c) is a bis- '(trialkyl)tin sulfide and (d) is a trialkylphosphite.

(tributyl)tin sulfide and (d) is tributylphosphite.

E v .w. rm I M...

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT No. 3,926,928 DATED December 16, 1975 INVENTOR(S) lglichglaie M. Karayarmis, Habet M. Khelghatian and am e c It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: 0

Column 3, Line 52 percentage should be percentages Colunn 5, Line 70 3.0/ll0.04/0.075 should be 3.0/l/0.04/0.075 Column 7,. Line 6 Et AlCl/TiCl BTS/IBP should be Et AlCl/TiCl /BTS/TBP On the Title Page: "Missak Khelghatian" should read 8 "Habet Missak Khelghatian" Signed and Sealed this ninth Day of March 1976 Q [SEAL] Attest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner oflarents and Trademarks 

1. A COMPOSITION WHICH COMPRISES: A. A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A TRIALKYL ALUMINUM, A MIXTURE OF TRIALKYL ALUMINUM AND AN ALKYLALUMINUM DICHLORIDE OR DIBROMIDE, A MIXTURE OF A TRIALKYL ALUMINUM AND A DIALKYALUMINUM CHLORIDE OR BROMIDE AND A DIALKYLALUMINUM CHLORIDE OR BROMIDE, B. TITANIUM TRICHLORIDE, C. AN ALKYLTIN SULFIDE, AND D. A TRIHYDROCARBYLPHOSPHITE.
 2. A COMPOSITION WHICH COMPRISES: A. A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A TRIALKYL ALUMINUM. A MIXTURE OF A TRIALKYL ALUMINUM AND AN ALKYLALUMINUM DICHLORIDE, A MIXTURE OF A TRIALKYL ALUMINUM AND A DIALKYLALUMINUM CHLORIDE AND A DIALKYL-ALUMINUM CHLORIDE, B. TITANIUM TRICHLORIDE, C. AN ALKYLTIN SULFIDE, AND D. A TRIHYDROCARBYLPHOSPHITE
 3. A COMPOSITION WHICH COMPRISES: A. A DIALKYLALUMINUM CHLORIDE, AND B. TITANIUM TRICHLORIDE, AND C. AN ALKYLTIN SULFIDE, AND D. A TRIHYDROCARBYLPHOSPHITE.
 4. The composition of claim 1 wherein (c) is a bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 5. The composition of claim 2 wherein (c) is a bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 6. The composition of claim 3 wherein (c) is a bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 7. The composition of claim 6 wherein (c) is bis-(tributyl)tin sulfide and (d) is tributylphosphite.
 8. A PROCESS WHEREIN PROPYLENE OR PROPYLENE AND AT LEAST 1 OTHER ALPHA-OLEFIN OF FROM 2 TO ABOUT 8 CARBON ATOMS IS CONTACTED BY AT LAST A CATALYTIC AMOUNT OF A COMPOSITION TO FORM HIGHLY-CRYSTALLINE POLYPROPYLENE OR COPOLYMER WHEREIN THE POLYPROPYLENE IS STILL SUBSTANTIALLY CRYSTALLINE COMPRISING: A. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A TRIALKYL ALUMINUM, A MIXTURE OF TRIALKYL ALUMINUM AND AN ALKYLALUMINUM DICHLORIDE OR DIBROMIDE, A MIXTURE OF A TRIALKYL ALUMINUM AND A DIALKYLALUMINUM CHLORIDE OR BROMIDE, AND A DIALKYLALUMINUM CHLORIDE OR BROMIDE, B. TITANIUM TRICHLORIDE, C. AN ALKYLTIN SULFIDE, AND D. A TRIHYDROCARBYLPHOSPHITE.
 9. A PROCESS WHEREIN PROPYLENE OR PROPYLENE AND AT LEAST 1 ALPHA-OLEFIN OF FROM 2 TO ABOUT 8 CARBON ATOMS IS CONTACTED BY AT LAST A CATALYTIC AMOUNT OF A COMPOSITION TO FORM HIGHLYCRYSTALLINE POLYPROPYLENE OR COPOLYMER WHEREIN THE POLYPROPYLENE IS STILL SUBSTANTIALLY CRYSTALLINE COMPRISING: A. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A TRIALKYL ALUMINUM, A MIXTURE OF A TRIALKYL ALUMINUM AND AN ALKYLALUMINUM DICHLORIDE, A MIXTURE OF TRIALKYL-ALUMINUM AND A DIALKYL-ALUMINUM CHLORIDE AND A DIALKYLALUMINUM CHLORIDE, B. TITANIUM TRICHLORIDE, C. AN ALKYLTIN SULFIDE, AND D. A TRIHYDROCARBYLPHOSPHITE.
 10. A process wherein propylene or propylene and at least 1 alpha-olefin of from 2 to about 8 carbon atoms is contacted by at least a catalytic amount of a composition to form highly-crystalline polypropylene or copolymer wherein the polypropylene is still substantially crystalline comprising: a. a dialkylaluminum chloride, b. titanium trichloride, c. an alkyltin sulfide, and d. a trihydrocarbylphosphite.
 11. The process of claim 8 wherein (c) is a bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 12. The process of claim 9 wherein (c) is a bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 13. The process of claim 10 wherein (c) is bis-(trialkyl)tin sulfide and (d) is a trialkylphosphite.
 14. The process of claim 13 wherein (c) is bis-(tributyl)tin sulfide and (d) is tributylphosphite. 